The interactive computer-based staircase scaling method was used in 2 experiments and the conventional scaling method was used in one experiment. All studies administered 3-sec duration heat stimuli ranging from 37 to 53 deg C. The first experiment used the interactive method to examine pain sensitivity in patients with cholestasis, a progressive liver disease. The hypothesis that the pruritus associated with this disease is due to increased levels of endogenous opiates was tested by both examining baseline experimental pain responses and assessing the effect of a challenge by a narcotic antagonist. A preliminary analysis of 19 patients showed no evidence for increased levels of endogenous opiates. The second experiment is providing additional evidence that cardiac chest pain in patients with normal coronary arteries does not represent general hyperalgesia and is actually accompanied by reduced somatic pain sensitivity. Thirty patients have completed the study and the code will not be broken until a total of 60 patients are completed. The third experiment is further characterizing the influence of "defensive" behavior on ratings of the sensory intensity and unpleasantness of pain sensations evoked by thermal stimuli. One hundred and eighty-five patients have completed the study. The results will be analyzed after 45 additional patients.